The present invention relates to a differential pressure regulating valve and also to a motor-driven compressor having the differential pressure regulating valve.
There has been known a scroll type compressor having a fixed scroll member and a movable scroll member. The fixed scroll member is formed integrally with the housing and has a scroll wall extending from the base plate of the fixed scroll member. The movable scroll member has a scroll wall extending from the base plate of the movable scroll member and is engaged with the fixed scroll member so as to make an orbital motion relative to the fixed scroll member. A fluid pocket as the compression chamber is formed by the scroll walls of the movable scroll member and the fixed scroll member. The volume of the compression chamber is reduced by the orbital movement of the movable scroll member thereby to compress the fluid such as refrigerant gas in the compression chamber. During the compression of refrigerant gas, the movable scroll member receives force acting in the direction that causes the movable scroll member to move away from the fixed scroll member due to compression reaction force of the refrigerant gas. Accordingly, the sealing between the fixed scroll member and the movable scroll member, or between the scroll walls and the base plates of the fixed and the movable scroll members is reduced. To prevent such reduction of the sealing, high-pressure refrigerant gas is introduced into a back pressure chamber which is formed on the back side of the movable scroll member, or on the opposite side of the movable scroll member from the fixed scroll member so that the movable scroll member is urged against the fixed scroll member by the pressure of the high-pressure refrigerant gas thereby to enhance the sealing.
Japanese Patent Application Publication No. 7-229484 discloses a scroll type compressor having a back pressure chamber formed therein so as to have a pressure that is higher than that of a low pressure region of the compressor, or a suction pressure region, and the pressure of the back pressure chamber is adjustable to a predetermined level by a differential pressure regulating valve as the pressure regulating valve. The pressure regulating valve is disposed in a bleed passage which is formed for connecting the back pressure chamber to the low pressure region of the compressor. The pressure regulating valve has a cylindrical valve chamber formed in the bleed passage, a valve hole formed upstream of the valve chamber with respect to the flow of refrigerant gas and forming a part of the bleed passage, a spherical valve body movably accommodated in the valve chamber and an urging spring adapted to urge the valve body in the direction that causes the valve body to close the valve hole. The pressure in the back pressure chamber is applied to the valve body in the direction that causes the valve body to open the valve hole and the pressure in the low pressure region is applied to the valve body in the direction that causes the valve body to close the valve hole. The bleed passage for connecting the downstream region of the valve chamber to the low pressure region extends from the lateral side of the valve chamber or the inner peripheral surface of the cylindrical valve chamber. Thus, when the pressure of the back pressure chamber becomes greater than a predetermined value, the pressure regulating valve opens the bleed passage. Therefore, the pressure of the back pressure chamber is prevented from being excessively increased.
According to the scroll type compressor disclosed in the above Publication, however, when the valve body of the pressure regulating valve opens the valve hole, the refrigerant gas introduced into the valve chamber through the valve hole flows around the valve body while flowing through a space between the peripheral surface of the valve body and the inner peripheral surface of the valve chamber. Then, the refrigerant gas is flowed into the bleed passage which is formed extending from the lateral side of the valve chamber. When the refrigerant gas flows into the bleed passage, an irregular flow of the refrigerant gas occurs in the valve chamber and the valve body is moved or displaced in a direction that is perpendicular to the extension and compression direction of the urging spring, thereby causing a turbulent flow of the refrigerant gas in the valve chamber. As a result, the refrigerant gas is vibrated and abnormal noise is generated, accordingly. When the pressure regulating valve is operated due to a differential pressure across the pressure regulating valve just after the compressor is stopped, noise unpleasant to the user of the compressor is generated.
The present invention is directed to providing a differential pressure regulating valve which prevents irregular flow of fluid occurring in the refrigerant flow when the differential pressure regulating valve is opened and also to a compressor having such differential pressure regulating valve.